The present invention relates to a charging device, for example, a charging device which charges a portable device via a universal serial bus.
In recent years, charging of portable devices via a USB has been becoming common. With USB2.0, the maximum current that can be taken out from a port is defined as 500 mA, and there is a problem in which it takes a while to charge a high-capacity secondary battery.
To address such problems, there is proposed a mechanism which can determine the power supply ability of the USB charger (host) side and obtain a current exceeding 500 mA from a charger having sufficient power supply ability (Japanese Patent No. 4695220 (Patent Document 1), Japanese Patent No. 4664362 (Patent Document 2), U.S. Pat. No. 7,581,119 B2 (Patent Document 3), Japanese Patent No. 3811704 (Patent Document 4), U.S. Pat. No. 7,170,259 B2 (Patent Document 5), Japanese Patent Laid-Open No. 2005-6497 (Patent Document 6), and Battery Charging v1.2 Specification, Internet <URL: http://www.usb.org/developers/devclass_docs> (Non-Patent Document 1), for example).